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The way a gecko's feet function has been a captivating but now relatively well understood phenomenon. They have many small spatula on the feet that exploit electromagnetic van-der-Waals forces on the walls to which they stick.

This concept has been developed in "nano-tape" a product which is adhesive the same way a gecko's feet are. And there has been no shortage of folks trying to create "spiderman gloves" to re-create this, one interesting example being this attempt by Elijah Animates to scale a flat rock climbing wall.

Elijah found that the nano-tape gloves were rendered ineffective by chalk dust on the wall which would coat the micro-structures and prevent them from sticking.

This leaves me very confused. I have often seen geckos when I travel to India in some extremely dusty conditions. For example, far MORE dusty than a well chalked climbing wall. Despite that, these geckos STILL stick perfectly well to all manner of surfaces, even glass walls.

Question:

What are gecko's feet doing that is fundamentally different than the nano-tape which allows them to operate in extremely dusty environments successfully? It clearly goes one step beyond merely exploiting the Van Der Waals forces but also somehow "removing any debris that is stuck".

This I also find hard to explain because I don't think I have ever seen a gecko "shake its legs off" similar to how a dog shakes water off. The mechanism of debris removal is probably subtler than that.

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This is a very interesting question. Basically (and this is the short answer), geckos possess a unique self-cleaning mechanism in their feet which synthetic nano tapes do not have. This capability allows geckos to maintain their adhesive properties even in dusty environments.

Gecko Feet Mechanism

Gecko feet are covered with millions of microscopic hair-like structures called setae, which branch into thousands of even smaller spatulae. These structures allow geckos to adhere to surfaces through Van der Waals forces, which are weak intermolecular forces that become significant at the nanoscale. When a gecko walks, the lateral movement of its feet creates friction that dislodges larger dirt particles, while smaller particles fall into the folds of their skin, effectively cleaning the setae as they move. The self-cleaning ability of gecko feet is attributed to the hierarchical structure of the setae and spatulae, which allows them to dislodge contaminants efficiently. Experimental studies show that geckos can regain about 80% of their adhesive strength after just a few steps on contaminated surfaces, thanks to this mechanism (see references 1, 2 and 3 for more details).

Synthetic Nano-Tape Comparison

In contrast, synthetic nano-tapes inspired by gecko feet often lack the same level of self-cleaning efficiency. While they can mimic the adhesive properties of gecko feet, they typically do not perform well in dusty conditions. The synthetic versions may rely on larger microhairs that do not effectively roll off dirt particles, leading to a significant loss of adhesive strength after contact with contaminants. Moreover, many synthetic adhesives use glue, which can degrade over time and lose adhesion, unlike gecko feet that remain sticky without any additional substances. Although some synthetic tapes have been developed to replicate the self-cleaning effect, they have not yet matched the natural efficiency of gecko feet in real-world conditions.

Conclusion

In summary, the fundamental difference lies in the gecko's natural ability to maintain adhesion through a sophisticated self-cleaning mechanism facilitated by its unique micro- and nano-structured feet, whereas synthetic nano-tapes often struggle with dirt retention and adhesive longevity due to their reliance on larger structures and glue-based adhesion methods (see references 4 and 5 for more details).

References:

  1. Robust self-cleaning and micromanipulation capabilities of gecko spatulae and their bio-mimics
  2. Gecko adhesion: evolutionary nanotechnology
  3. Dynamic self-cleaning in gecko setae via digital hyperextension
  4. Robust self-cleaning and micromanipulation capabilities of gecko spatulae and their bio-mimics
  5. Carbon nanotube-based synthetic gecko tapes
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    $\begingroup$ I don’t usually read or vote on organismal biology questions or answers because their quality is generally low, but this is an example of a first-rate answer to a perceptive question. We could do with more. $\endgroup$
    – David
    Commented Sep 3 at 18:23
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    $\begingroup$ Thanks for the great answer. $\endgroup$
    – Fattie
    Commented Sep 5 at 14:05

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